566 Dr. M. Hartog. [ Dec. 1, 
5. The fibres of the cell-spindle and astral rays are of the nature of 
chains of force; their production by outgrowth of differentiated cytoplasm 
from a centre is different to that by simultaneous segregation of the 
magnetic chains in a mixture of magnetic dust and liquid, etc., under the 
condition of the experiment (but see note to p. 557). We can, however, 
utilise the study of the physical properties of magnetic chains, and apply by 
analogy many of the results to the cell-chains. 
6. Thus, magnetic chains of force (a) anastomose and (b) interlace at 
adjacent levels as cell-chains are found to do. 
7. The straight or backturned radiations of the astral rays are repeated in 
the magnetic models if we put in place of the outer cytoplasmic membrane 
(Hautschicht) an envelope permeable to magnetism (see 3, d). 
8. A disc of iron put in front of a crescentic pole-piece gives the same 
field as the nucleus in the hollow of a single crescentic centrosome (see 3, c). 
9. The axial section of a spiral cell-field may be modelled magnetically if 
we use a mixture of magnetic dust in a viscid medium, and rotate it over a 
pair of unlike poles. From this we infer that other forces than mitokinetic 
are operative in the dividing cell, where such figures are seen. 
10. The separation of the poles of the cell figure must be also due to other 
forces, and the effect of their traction against that of the spindle is sometimes 
exceptionally well seen in the occurrence of “ blobbed” centrosomes. 
11. We can obtain a triaster (and combinations implying the triaster) of 
three poles joined by consecutive spindles by the action of three centres, two 
poles of opposite sign, and the third of zero sign—in the models the core of 
a magnet without a coil. These figures may be extended by additional centres 
to “ fill space.” 
12. In most multipolar cell-figures the poles are so distributed as to produce 
the maximum of spindle connections. 
13. We can produce a figure of four poles united by spindles to a common 
centre of opposite sign or at zero; this is the analogue of the tetraster about 
a central mass of chromosomes (see 3, ¢). 
14. Chains of force, ike movable magnets, tend to move into the strongest 
part of the field; thus if we form a magnetic spindle in glycerine, the lateral 
chains tend to sway or drift in towards the axis, becoming shorter and denser, 
the clear lateral space from which they have receded corresponds to 
“ Biitschlo’s Space” in the cell. 
15. The separation and discession of the sister segments of the chromo- 
somes from the equator to opposite poles is such as would take place under the 
action of a dual force, and can be reproduced in our model (see 3, @). 
16. A spindle figure can only be obtained in a field with the two unlike 
ae 
